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Difficulty: HardMulti-AZ, Multi-Region Architectures and Disaster Recovery (DR)

A SaaS payroll company hosts its platform in the us-east-1 Region. The architecture consists of Amazon EC2 instances in an Auto Scaling group behind an Application Load Balancer (ALB), and an Amazon RDS for PostgreSQL database. The company needs to design a disaster recovery (DR) plan in the us-west-2 Region. The solution must support a Recovery Time Objective (RTO) of 1515 minutes and a Recovery Point Objective (RPO) of 55 minutes while minimizing running infrastructure costs in the secondary Region during normal operations.

Which combination of actions should the solutions architect implement to meet these requirements? (Select TWO.)

  1. Create an Amazon RDS cross-region read replica in the secondary Region, and promote it to a standalone DB instance during a failover event.Answer
  2. Create an Auto Scaling group in the secondary Region with a desired capacity of 0, and configure it to scale up using a pre-baked Amazon Machine Image (AMI) during a failover event.Answer
  3. C
    Deploy a scaled-down Auto Scaling group with a minimum capacity of 2 small EC2 instances in the secondary Region to constantly run and monitor the database.
  4. D
    Configure an Amazon Route 53 latency-based routing policy to automatically redirect application traffic to the secondary Region during an outage.
  5. E
    Export automated database snapshots to Amazon S3 Glacier Flexible Retrieval in the secondary Region, and restore the database during a failover event.

Answer

Create an Amazon RDS cross-region read replica in the secondary Region and promote it during failover, and create an Auto Scaling group in the secondary Region with a desired capacity of 0 that scales up using a pre-baked Amazon Machine Image (AMI) during failover.
To meet the RPO of 5 minutes, data must be continuously replicated to the secondary Region. Amazon RDS cross-region read replicas use asynchronous replication to achieve replication lags of just a few seconds. During a failover, the replica is promoted to primary. To achieve a 15-minute RTO while minimizing running costs, a Pilot Light architecture is used. By deploying an Auto Scaling group in the secondary Region with desired capacity set to 0, no compute instances run or charge during normal operations. Upon failover, the Auto Scaling group desired capacity is increased, spinning up instances from a pre-baked AMI in minutes.

Step-by-Step Solution

1
Configure database replication to meet RPO.
An Amazon RDS cross-region read replica is created in us-west-2, replicating data asynchronously with a lag of seconds, satisfying the 5-minute RPO.
Asynchronous cross-region replication is required because snapshot copies would take too long and fail the RPO target.
2
Configure secondary compute resources for cost optimization.
An Auto Scaling group is set up in us-west-2 with desired capacity set to 0.
Setting the capacity to 0 prevents any running compute costs while idle, aligning with the Pilot Light disaster recovery strategy.
3
Define the failover orchestration steps.
In a failover event, promote the RDS read replica to a primary instance, update the Auto Scaling group capacity to launch instances from the pre-baked AMI, and update DNS records.
This process takes less than 15 minutes, successfully meeting the RTO target.

Key Concept

Implementing a cost-effective Pilot Light disaster recovery strategy using cross-region database replication and on-demand compute provisioning.
Estimated Time:2m 30s
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Topics

Multi-AZ, Multi-Region Architectures and Disaster Recovery (DR)

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